M1156

Copyright ©  2003  Regents of the University of Minnesota. All rights reserved.

Purpose

The purpose of this manual is to provide an overview of weed control for the establishment and growth of trees. Special attention is paid to inclusion of non-chemical as well as chemical methods. The methods and chemicals described are not all-inclusive. While the techniques described may not change, many of the chemical names and labels change frequently; therefore, always refer to the label for specific application methods, rates and use. The use of brand names in this document is not an endorsement of a particular brand; brand names are provided for information that can be quickly used. Most herbicides used in forestry are available for use by the landowner. A few restricted-use herbicides require a private pesticide applicators license. These are noted in the text.

While not required, landowners are encouraged to attend pesticide applicator training courses available periodically throughout the state. Please visit the pesticide applicators website at http://www.extension.umn.edu/pesticides/. To view sample labels for each chemical, you can visit the CDMS website at http://www.cdms.net/.

Organization

This guide is organized in sections: weed ecology, weed growth and sensitivity, site preparation and maintaining your plantings. Nothing beats a good plan for dealing with weeds before the problem arises. Removing weeds after the trees have been planted is often more costly than reducing the likelihood of weed emergence before planting.

Weed Ecology

By definition, a weed is a plant growing in the wrong place. Weeds in forestry can kill newly planted trees and reduce growth. Control of weeds is based on an understanding of their lifecycle, their basic biology and their growth requirements. Weeds, as with other plants, are categorized as annual, perennial or woody plants.

Annuals

Annuals complete their lifecycle in one year. Annuals are divided into two general classes, summer and winter annuals. Summer annuals overwinter as seeds and emerge in spring. Winter annuals overwinter as seedlings or root systems. Because of the developmental differences between winter and summer annuals, the timing for control will differ for these sub-categories of plants.

Grasses

Annual grasses fall into two general classifications, warm and cool season. These two grasses have very different responses to herbicide treatment because their photosynthetic pathways (the ways they produce food) are different. Grasses are monocots and the growing points of many are at or below the soil surface. Due to the location of the growing point, grasses can be mowed with little or no damage to the plant. It is this characteristic that makes mowing of little benefit in killing grasses where many broadleaves may have been killed.

Broadleaves

Annual broadleaves are divided into two main classifications, epigeal and hypogeal. The cotyledons of epigeal plants emerge from the ground and act as leaves (seed leaves). This is apparent on many plants, such as beans and sunflowers. The cotyledons of hypogeal plants stay below ground. This is apparent in such plants as oaks. In general, epigeal plants are more susceptible to aboveground damage than hypogeal plants. In many cases, mowing of hypogeal plants increases their dominance.

Perennials

Perennials are weeds that live two or more years. A plant that completes its lifecycle in two years is a biennial. Plants that take longer are generally classified as perennials.

Grasses

Grasses reduce tree growth or inhibit tree establishment due to competition for moisture and nutrients. Perennial grasses reproduce sexually (seed formation) and asexually (send out underground stems or roots that form another sprout). In many cases, plants of seed origin and plants that originate asexually (sprouts, tillers or regrowth after cutting) react differently to herbicides. For example, after being mowed, plants originating asexually are harder to control with herbicides. In addition, perennial grasses often take several years to establish or produce seed. For this reason, they can go somewhat unnoticed until it is too late.

Broadleaves

Perennial broadleaves often have very significant below ground storage of nutrients. Bulbs, large taproots, tubers and corms are all examples of these methods of nutrient/water storage. After establishment, which is often slow, they can be difficult to kill in established tree plantings.

Woody Plants

In addition to herbaceous plants (those that kill to the ground every winter), tree farmers also have to reduce competition from woody vegetation. Woody vegetation is defined as any plant that has persistent, over-wintering, aboveground stems. Common examples are hazelbrush, sumac and willow. Woody vegetation is often characterized by taking many years to establish. Because of the ability of woody vegetation to store nutrients below ground and to coppice (resprout after cutting), most woody vegetation is difficult to kill without herbicides. Often, after harvest of established stands, understory weeds like hazelbrush and prickly ash can become the dominant site cover. In other cases, plants that coppice well like poplar or those with fast initial seedling growth like fire cherry dominate the site. Therefore, post-harvest tree establishment should be planned before harvesting occurs because it is easier to control unwanted woody vegetation when your new seedlings are not on the site.

Weed Growth and Sensitivity

Germination and Fresh Germinants

In order to germinate, some seeds need to be “stratified”, encounter a “cue,” be “scarified”, or meet with any of a complex mix of needs. “Stratification” is generally a requirement of a certain number of cold days or days below a certain temperature. A “cue” is an environmental condition, like a pulse of nitrogen or water that initiates germination in the seed. “Scarification” is the physical, chemical or biological damage to the seed coat (outside skin of the seed) that allows water to enter and the seed to germinate. Without the appropriate cues the seed will remain dormant.

Germination is a very sensitive time for many weeds. Many pre-emergent herbicides work to interrupt the germination or to damage the plant immediately after germination.

Several other ways exist to use germination requirements for advantage in weed control. Repeated tillage every few weeks the year prior to planting trees (called “keeping the ground black”) will induce germination of weed seeds, particularly annuals. The seedlings will be destroyed in the next tillage. This technique can deplete the seed bank and result in fewer weeds the year of planting.

Another option is to limit soil disturbance, a significant cue to annual weeds, the year of planting. This has been shown to significantly reduce weed germination. Reducing soil temperature by mulching or reducing light that reaches the soil has also been shown to have some success.

Smother crops are another way to reduce the germination success of weed seeds. Smother crops are highly competitive crops, like buckwheat, that simply outcompete the weeds the year prior to tree planting.

Seedlings

After emergence, many plants go through a period of slow growth. This is a very sensitive period for weeds. For most weeds, this is the period when they are most easily killed by tillage, mowing, flame or steam weeding and foliar/contact herbicides. This is particularly true for epigeal broadleaves and shallow-rooted weeds.

Rapid Growth Phase

After passing from the seedling phase into the rapid vegetation growth phase, weeds begin to use large quantities of water and nutrients. The function of this stage for the plant is to increase its competitive status and to acquire nutrients for reproduction. At this stage, post-emergent herbicides and some systemic herbicides (those that are absorbed and relocated by the plants) are most effective. Weeds that are very small and unnoticed can increase dramatically in size and competitive status at this stage. Many types of non-chemical treatments lose effectiveness at this phase because weeds have become deeply entrenched and have stored a considerable quantity of nutrients.

Reproduction

The rapid growth phase often begins to decline with the first flowering. This is particularly true of annual and herbaceous perennials and less true of woody vegetation. During this stage, many herbicides are no longer effective because plants are only taking up small quantities of water and nutrients; however, some systemic herbicides function best in the early reproductive stage. Mowing and tillage are often very effective in the early part of this stage because the plants are no longer growing rapidly and the physiology of the weed has changed to reproductive. Annual weeds often will not resprout if cut at this stage. If the annual weeds have flowered and seeds are still forming, however, seed development may still occur after being cut from the plant and these seeds may still have the ability to sprout.

Fruiting

The seed is usually the least sensitive part of the plant. It can tolerate the worst droughts as well as hotter and colder temperatures than at any other stage. Some species of weed seeds have been shown to remain viable for more than 100 years. Keeping the weed in this stage is often one of the best ways to control weeds. This is how many mulches work.

Site Preparation

Site preparation prepares the site for tree planting by reducing the number of weeds or reducing the future growth of weeds.

Unless a planting site has just come out of annual crops like corn and beans, the site is likely to have an established community of weeds. The composition of this community is usually relative to the length of time since a major disturbance. Freshly disturbed sites often have simpler communities (composed of annuals and some perennials), while older sites may be dominated by many species of perennials and woody plants.

Site Preparation for Sites Dominated by Herbaceous Plants

When a site is dominated by competitive annual and perennial weeds, it is often necessary to control these plants prior to tree planting in order to speed establishment of the trees. This provides the dual purpose of allowing the trees a quicker start and eliminating the need for future weed control. Even when a site has come out of conventional cropping with a limited weed seed bank, use of a site preparation herbicide can be justified. The goal of site preparation treatments is to kill established weed communities, limit weed seed germination, or to encourage germination prior to planting when weed control is less complicated.

Site preparation treatments to control vegetation primarily fall under the headings of smother crops, tillage, brush cutting, grazing and herbicides.

Smother Crops (Agroforestry)

Smother crops are plant species seeded into a site that will effectively out-compete most annual weeds. Smother crops are effectively used when seeded shortly after a tillage. For obvious reasons, this system is more adapted to recently abandoned agricultural land than to recently harvested forestland. Tillage of the soil surface often encourages the germination of annual weed seeds present in the soil (the soil seed bank). The presence of a very competitive cover crop causes these weeds to be out-competed and, therefore, non-reproductive. This technique has been applied with success in some agricultural systems, particularly organic vegetable crops. An additional benefit of smother cropping is a potential harvest of forage or seed from the site prior to tree planting. Numerous potential species can be used as a smother crop; however, care should be taken to use compatible species. For example, rye can produce allelopathic chemicals (a type of herbicide that plants use to kill other plants). The allelopathic chemicals make the plant a wonderful smother crop but a potential problem if trees are planted too soon after the crop is plowed under. Potential species for use as smother crops are listed in Table 1.

Tillage (Agroforestry)

An often heard comment is that if you “keep it black (note: this means till it after every flush of weed growth) the year before planting trees, you will be fine.” This is true to an extent. Tillage kills the sprouted weed seeds and reduces the health or kills the perennial weeds. Additionally, tillage encourages the annual weed seeds in the soil (the seed bank) to germinate. At the next tillage, they are destroyed without reproduction. This serves to significantly reduce future weed infestation. Often a smother crop would have functioned as well at a lower cost. The main concerns with this are:

1. Repeated, diligent cultivation is needed; if weeds are allowed to reproduce between cultivations, the problem can be worse than before.
2. Soil erosion by both wind and water can be fairly high under this system.
3. Costs of tillage add up, especially during high moisture years.

A minimum tillage depth of two inches is necessary to realize the benefits of this technique. In areas with overall low annual precipitation, this repeated shallow tillage can allow accumulation of soil moisture that can help during the establishment year for the trees.

Site Preparation for Sites Dominated by Both Woody and Herbaceous Weeds

In forestry plantations following harvest and reclamation of abandoned agricultural or grazing land, brush control is of prime importance to stand establishment. Numerous options exist for site preparation. A few of the main methods are discussed below.

Option 1: Tillage

On fairly recently abandoned agricultural land where brush/trees are less than two inches diameter at ground level, moldboard plowing (possibly followed by an application of herbicides listed in Table 3 after re-sprouting) may be sufficient.

Option 2: Brush Cutting (no herbicide)

Many pieces of machinery are available for cutting brush, and most function satisfactorily; however, sprouting following cutting is often intense. Brush cutting immediately after leaf out (mid-June) will reduce nutrient reserves in the brush roots, limiting the vigor of the resulting sprouts. Repeated brush cutting as soon as the sprouts reach approximately six inches can provide effective control, although it is very time consuming.

Option 3: Brush Cutting (with herbicide stump treatment)

Cut brush as with option two and spray cut stumps with herbicides from Table 2. Several machines are available which either wick or spray herbicides as the brush is cut. For managers of large plots, these are very effective and time-efficient.

Option 4: Brush Cutting (with herbicide sprout treatment)

Cut brush as with option two; allow stumps to resprout and then treat with herbicides from Table 3.

Option 5: Site Preparation Herbicide Application

Several herbicides are available for foliar application without brush cutting. These are included in Table 4 for conifer plantations and Table 5 for hardwood plantations. Please note that your herbicide choice depends on both species of the weed and species of the future trees; please refer to Table 4.

Option 6: Girdling Without Herbicide

Sometimes many larger stems exist on the site to be regenerated. Girdling, the removal of a band (or bands) of bark all the way around the tree, cuts off or reduces the flow of nutrients to the tree and the tree slowly dies. This can be effective with some species; however, many of the weedier brush species will resprout from the stump/roots. Several mechanical systems exist for girdling trees. These can include gasoline-powered girdlers, chainsaws run just through the inner bark, girdling knives, hatchets, and even torches. As all of these tools can cause significant injuries to the applicator, great care is suggested in their use. To help assure a more effective kill, the inner bark should be removed continuously around the tree in a band at least one inch wide. If possible, two bands will help assure a more effective kill.

Option 7: StumpTreatment, Stem Injection or Basal Application

As with girdling, larger brush species can be controlled using small amounts of chemical applied to the cut stump, injected into the plant or applied to the stem of the plant. Potential herbicides used with these application methods are listed in Table 2.

This method is used to reduce sprouting and regrowth of woody brush and trees after the brush and trees have been cut. A variety of chemicals can be used. For best results, treatment of the stump should occur immediately after cutting. A list of herbicides used for stump treatment is listed in Table 2. The rates and method of application will be included on the label. In most cases the herbicide can be mixed and carried to the site in a backpack sprayer or smaller spray bottle.

If the tree/brush is not to be cut, either a “stem injector,” an “injecting hatchet” or a regular hatchet and a spray tank may be used. Stem injectors inject a pre-measured dose of herbicide into the plant. Injecting hatchets have a tube that applies herbicide as the hatchet is used. Alternatively, a regular hatchet may be used to make a cut and the herbicide can be applied in the same manner as with the cut stump treatment.

Basal bark, low volume basal bark and thinline treatments require a backpack sprayer or smaller. These treatment methods provide an extended season of application from early spring through early winter.

Basal bark treatment uses the lowest concentration of herbicide. It is applied to all sides of the lower 15 inches of tree trunk. This method can be used on trees of all sizes.

Low volume basal bark spray is similar to basal bark treatment with two differences. The concentration of herbicide is higher and the size of tree that can be treated is limited to trees of six inches in diameter at the base. Since the concentration of chemical is higher, less volume of chemical is used.

Thin line treatment, also known as ultra low volume application, is used on trees of less than six inches in diameter at the base. A thin stream of undiluted or highly concentrated herbicide is applied in a horizontal line around each stem. Approximately 2 to 15 milliliters of undiluted herbide is used per stem. It is recommended that a meter be used to regulate the amount of chemical used. A metering device is commercially available and can be ordered from most spray equipment dealers.

Option 8: Grazing

If brush is fairly small, intensive grazing of the site can be used over the course of two or three years to reduce the presence of brush. While sheep, cattle and even pigs can be used to some advantage, experimentation has shown highly variable levels of success in brush control. Grazing/browsing of goats over the course of two or more years, however, can be a very effective method of brush control. The use of livestock in brush control, while potentially effective, is still experimental.

Option 9: Others

Fire, drum choppers, dozers and other potential methods of brush control exist. While fire is still widely practiced in many states, especially the southeastern United States, liability issues (especially if fires escape or smoke blows through an urban setting) are significantly decreasing the utilization of this tool. Drum choppers, dozers and other machinery have potential for use in some settings, but are still not very common methods. Hand or machine “grubbing” (removal by the roots) is also possible but extremely labor intensive and can cost hundreds of dollars per acre. Grubbing is only usually economically justified with highly competitive or invasive plants, high value sites (windbreaks, shelterbelts, etc.) or where all other options have failed.

Maintaining Your Plantings

Maintaining Your Plantings—Pre-emergence

Mulches

Use of mulches, with and without application of pre-plant herbicides, can be a very successful way of establishing trees. Mulches serve as a barrier to weed growth. Additional potential benefits of mulches can include conservation of soil moisture (most types of mulch), reduced erosion (most types of mulch) and increased soil temperature (black plastic and fiber mulches). The main faults with some mulches include reduced soil temperature (primarily with chips and straw), increased rodent damage (primarily straw and grass) and reduced nitrogen availability (primarily if organic mulches are incorporated into the soil through tillage). Overall, mulch can be a very cost effective weed management technique if the area that is mulched is small or if the cost of mulch is low (i.e., agricultural or forestry waste products).

Mulches fall into two general classifications, roll/mats and flowables. Fiber, plastic, cardboard and paper mats are becoming more common in agroforestry and windbreak applications. The more common “geotextile” type mats and rolls of mulch are usually made of synthetic fibers that can last several years in field applications. Rolled black plastic (approximately three mil thickness), common in vegetable production, is usually too fragile for application in tree planting. although is has been used successfully in low wind areas. Fiber mats, especially those developed for forestry applications, have been used very successfully, although there have been some reports of damage in high wind areas and due to feeding by deer (some mulch mats appear to be palatable to deer). Cardboard mats and recycled cardboard have also been tried with some success. The main limitation on use of tree mats and rolled mulch is the cost. Cost of rolled tree mats can often amount to more than a dollar per tree. Over a large plantation this can be a significant detriment. Recycled material, while cheaper, is usually very labor intensive to apply.

Flowables are another option for tree mulching. Byproducts of forestry and agriculture, such as hulls, straw, cobs, stalks, chips and leaves, are all potentially usable organic flowables. Cost of materials is often low, frequently available in rural areas free of charge or at a small delivery charge, but labor in application is high. Additionally, the persistence of flowables is usually low, leaving the trees open to competition after only a couple of years. In some cases, this may be sufficient; in others, reapplication of mulch will be essential. Use of some flowable mulches in high wind areas (for example, straw and hulls) is ill-advised; however, many authors have over-emphasized the movement of flowables after placement. While some movement is likely in the author’s experience, the first soaking rain storm to follow application limits future movement of the material. Information on mulches is included in Table 5, please note that material has been gleaned primarily from vegetable and horticultural production systems, with much less having been done with tree seedlings.

Cover Mulches/Living Mulches

Quite a bit of anecdotal (non-scientific) information exists on the use of cover crops in tree plantings. Surprisingly, not a lot of scientific research has been targeted at decision-making regarding which cover crop species to plant and how to use them for tree plantings. The essential benefits of cover crops/living mulches are primarily protecting the soil from erosion, possible weed control, nitrogen fixation (if legumes are used) and potentially a few others depending on the species of cover crop that is chosen. One additional benefit in the first year of planting is that the cover crop serves as a windbreak for the seedlings. The main problems associated with their use are that the cover crops serve as competition with the seedlings, provide habitat for rodents and may have some allelopathic effects (growth suppression caused by chemicals that the cover crop exudes). The way to gain the benefits of the cover crops without the problems is up to the tree planter’s creativity. A few ideas are included below.

Species—Numerous cover crops have been used with tree plantings. All are a compromise. Several organizations have been researching this issue for agricultural production. A few of their findings about species are shown in Table 7.

Methods of use:

1. Cover crops that are not winter hardy can be planted the year before to act as a mulch the following spring. Use of smother crops written about in previous sections is preferred. This is operational on some organic farms.
2. Winter-hardy cover crops can be killed within the tree row before or after planting but allowed to grow between rows. This is operational in many fruit orchards across the country.
3. Winter-hardy cover crops can be killed with mowing or herbicide and planted into as a mulch.
4. The cover crop can be sprayed with a sub-lethal herbicide dose to reduce the growth rate. This is used in Christmas tree plantations operationally in some states. While the application rate and height of plants at application varies with the species of cover crop, the application is usually early in the growth of the cover crop (less than six inches). The chemical most commonly used for the purpose is glyphosate at a dose of eight ounces per acre. Please see the chemical label for more specific information.
5. A winter-hardy cover crop can be planted into without any treatment. This is the least preferred; however, it can be used successfully in some situations. This is most successful when the cover crop is mowed at least three times a year.

Pre-emergent Herbicides

Many post-emergent herbicides also have pre-emergent activity; however, most pre-emergent herbicides are only suited to agroforestry plantings or aforestation (going from agricultural land to forestry) plantations. Some common agroforestry pre-emergent herbicides include pendimethalin (Pendulum), linuron (Lorox and Linex) and simazine (Simazine 90DF, only for shelterbelts).

Maintaining your Plantings—Post-emergence

Mowing

Mowing can be an effective way to control many broadleaved herbaceous and small woody plants; however, grasses and hypogeal/coppicing broadleaf and woody species are competitively favored. This can also complicate future control of some grasses. Mowing grass can move it from the seedling stage into the rapid vegetative growth stage, limiting the effectiveness of some vegetation control methods. Mowing to control broadleaves should be timed to either cut the plants when they have expended most of their energy on a new flush of growth (for perennials this is often mid- to late June) or when they have switched to their reproductive stage (for annuals). If cutting is delayed until after partial seed set, many species will still be able to produce viable seed. In many cases, however, mowing is one of the easiest ways to reduce the size of the vegetation so that tillage, etc., can be conducted without seedling injury.

Grazing

Grazing for weed control has as many proponents as opponents. For post-emergent control, timing of grazing is of great importance. Geese, sheep and cattle have been used with some success in conifers. The animals should not be allowed on site until the candles (fresh conifer growth in spring) have begun to harden. The forage quality of conifer needles is low enough that many animals will not consume very many of them unless adjacent herbaceous vegetation is of very low quality. Damage due to rubbing and feeding can range from very limited to almost total destruction. For this reason, care should be taken. Effective control of competing hardwoods in pine plantations (release of conifers from hardwood competition) has been seen in several states and this is probably the most successful potential application of grazing for weed control. Most likely, rotational or cell grazing might be better than open pasturing.

Tillage

Tillage between rows of trees is very common in agroforestry-type plantings. This is often very cost effective. Tillage is easier when weeds are small. Control becomes progressively harder as the weeds mature. One unfortunate side effect of tillage is that annual weed seeds are induced to germinate when the soil is tilled. These weeds must then also be controlled until either the tree canopy shades out the weeds or trees begin to dominate the site. There is potential for soil erosion, if excessive tillage is used. In rocky soils, the potential to “bring rocks to the surface” also exists, making future mowing of the site unpleasant for the operator.

Flame/Steam Weeding

Another experimental technique is flame or steam weeding. The temperature of the weeds is raised by the use of steam or flames until damage occurs. The goal is not to “burn up” the weeds, just to slightly “cook” them. This is a very experimental technique with many problems, not the least of which is potentially killing all the trees; however, it holds quite a bit of promise.

Rope Wicks/Sponge Applicators, etc.

When the weeds have gotten tall enough that they greatly exceed the height of the seedlings, using a rope wick can help control weeds with limited tree damage. A rope wick uses a systemic herbicide, usually glyphosate. The applicator, essentially a horizontally suspended “rope wick” or a handheld “wiper,” is pulled over the top of the weeds or touched to the individual weeds. The herbicide is directly applied to the weeds with nearly no off-target application. With rope wicks being pulled over the tips of the tall weeds with much shorter trees, the trees have little or no contact with the herbicide. If used correctly, rope wicks can isolate the majority of the damage to the weeds.

Herbicides Release

After weeds have emerged, the trees must either be shielded from the herbicide, sprayed over when dormant or be resistant to the herbicide. Shielded spray can be used with agroforestry-type plantings very effectively because the trees are usually planted in straight measured rows. Shielded spray can also be used with small plantings where the applicators spray around individual trees. For forestry-type plantings, this is usually not practical. Instead, herbicides are either applied when the trees are dormant or over resistant trees. Herbicides that are commonly used for “release” from brush or herbaceous weeds in conifer stands include 2,4-D (2,4-D LV4™ ² and Patron 170™ ³), triclopyr (Garlon 3A™ ⁵ and Garlon 4™ ⁵), glyphosate (Glypro™ ⁵ and Accord™ ⁶), hexazinone (Pronone 10G™ ¹⁰, Velpar L™ ¹¹ and DF™ ¹¹), and imazapyr (Arsenal AC™ ⁷). Please see label instructions and Table 8 (.pdf document) to determine timing of application and tree sensitivity. Sensitivity to herbicides is often dependent on the timing of application. When dormant, conifers are relatively insensitive to many herbicides. During active growth of the candles, many herbicides that are safe at other times of the year are unsafe. Herbicides that can be used in some hardwood plantings for release from woody or herbaceous competition include sulfometuron methyl (Oust™ ¹¹), clopyralid (Transline™ ⁵), fluazifop (Fusilade™ ¹³), and quizalofop (Assure II͐ ¹¹). Once again, please see the label.

Tank Mixing

One other issue to consider is tank mixing. Tank mixing is the addition of more than one pesticide to the spray solution. For example, glyphosate (Accord™ ⁶) and sulfometuron methyl (Oust™ ¹¹) are tank mixed for fern control as a site preparation. It is important to remember to add 1/4 to 1/2 of the liquid to the tank, add the powders, then the liquids/flowables. Agitate and then add the adjuvants, oils and surfactants last (these are chemicals that are added to improve the effectiveness of the chemicals and will be called for on the label if needed).

Conclusion

Selection of appropriate weed control methods prior to tree planting is essential to plantation success. While many methods exist, the complex of site characteristics and time of year and weed species present dictates which are likely to be successful and which will likely fail. If chemical options are selected as a part of the weed control program, we highly recommend that you consult with a forestry professional familiar with weed control options. We also recomend that prior to using herbicides you take the Private Pesticide Applicators Training. While this training is not required for private use of many of the chemicals listed, it is still quite useful. It is essential that you read the whole label prior to use of any chemical. The label includes information on timing, selection of rate and parameters that will dictate success or failure. Inappropriate use of herbicides can result in site contamination, death of desired plant, increased dominance of problem weeds, and personal injury.

You will need Adobe Reader to view and print Table 8 and Table 9. To download the Adobe Reader free, click the link to the left.

Table 8. Herbicides for Use in Release (.pdf document)

Table 9. Herbicide Brand Names, Chemicals, Target Species and Uses (.pdf document)

Endnotes

Special thanks to Louanne Brooks, Dow AgroSciences; Norm Krause, farmer and Director of the Central Lakes College Agricultural Center; Steve Welliver, the Wellson Group; Bob Stommes, Regional Extension Educator, University of Minnesota Extension Service; LaVonne Blackwell, former Administrative Assistant, University of Minnesota; and, Sophie Demchik, Natural Resource and Sustainable Farming Consultant, for their review and input on this document.

In accordance with the Americans with Disabilities Act, this material is available in alternative formats upon request. Please contact your University of Minnesota Extension office or the Distribution Center at (800) 876-8636.

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